What is a crazed glaze?

Glaze crazing or glaze crackle is a network of lines or cracks in the fired glazed surface. It happens when a glaze is under tension. A craze pattern can develop immediately after removal from the kiln or years later.

What causes glaze crazing?

Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the clay body during cooling. Because glazes are a very thin coating, most will pull apart or craze under very little tension. Crazing can make a food safe glaze unsafe and ruin the look of the piece.

How do you fix crazed glaze?

Adding Silica and Clay to Reduce Crazing

There are several ways to correct crazing. However, changing only one material may change the appearance of the glaze, making it more glossy or matte. A reliable method is to increase both the silica (flint or quartz) and clay in the ratio 1.25:1 silica to clay.

What does crazing look like on pottery?

Have you ever seen a piece of pottery where the surface looks like it's covered with a spider web of tiny cracks? That's called crazing. They are not cracks in the actual piece of pottery but rather surface-level cracks in the fired glazed of the piece.

What does crazing mean in ceramics?

Crazing refers to the formation of a network of fine cracks on the surface of glazed ceramics caused by tension between the ceramic body and the glaze. This process can come about in a number of ways.

Crazing (food safety in glaze)

Is crazing OK on pottery?

Generally, crazing is considered a glaze defect because the vessel can be significantly weaker than an uncrazed pot. Craze lines can also harbor bacteria or germs. Therefore, dinnerware pottery should be uncrazed ware.

What is the difference between cracking and crazing?

Craze cracks on concrete is when the surface of concrete develops a lot of fine cracks. Sometimes called map-cracking or alligator cracking, crazing of concrete is a result of conditions and curing methods at the point the concrete is laid or even the way it is finished.

Is crazing a defect?

Crazing is a glaze defect of glazed pottery. Characterised as a spider web pattern of cracks penetrating the glaze, it is caused by tensile stresses greater than the glaze is able to withstand.

How do you check for crazing?

Crazing appears when ceramic is cooled and the glaze shrinks more than the clay to which it is rigidly attached. Shivering, on the other hand, usually first appears when ware is suddenly heated.

Does crazing make pottery not food safe?

Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces. Crazed ceramic glazes have a network of cracks.

Does crazing reduce value?

The presence of crazing usually diminishes the value of objects but it can depend on the severity of the damage and rarity of the crazed piece.

Are crazed mugs safe?

Coffee mugs usually develop scratches over time but they are still safe to use. Crazing inside the mug may cause harmful trace elements from the leach into the drink. The glaze is likely to chip around the crazed areas and the fragments can mix with the drink and end up being ingested.

Can cold temperatures cause crazing?

It is upon the cooling of the kiln and the contraction of the wares that cracks form. Heating and then cooling too rapidly can cause the glaze to shrink too quickly and cracks appear more readily.

Can you use dishes with crazing?

Crazing on dinnerware pieces is never okay

Sometimes, this is true. There are certain ceramic techniques like those used to produced Raku ware where the network of fine lines is a desired decoration technique. This is not the case for fine English dinnerware.

What does crazed glass look like?

Crazing is a web of tiny cracks that can appear on the lenses of eyeglasses coated with an anti-reflective coating. Looking through crazed lenses can make your world appear blurry.

Why is my glaze cracking while drying?

When a glaze cracks as it dries on a pot, it usually means that the glaze is shrinking too much. This is normally caused by having too much plastic material (ball clay) in the glaze. If this is the problem, it should exist from the beginning (not appear two months later).

How is crazing caused?

Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the body during cooling. Because glazes are a very thin coating, most will pull apart ar craze under very little tension. Crazing can make foodsafe glazes unsafe and ruin the look of a piece.

What is crackle glaze?

A type of ceramic glaze that is intentionally crazed. Crazing is a crack pattern caused by thermal expansion mismatch between body and glaze. After the glaze solidifies (as the kiln cools) it shrinks more than the body. To relieve the tension of being stretched, it cracks.

What is the crazing?

Crazing refers to a network of visual cracks on a coated metallic surface. It occurs due to tension stresses in some glassy thermoplastic polymers. Crazing is propagated in metallic surface regions that experience high tension and leads to the formation of microvoids and small cracks.

How do you clean crazing?

Use Oxygen Bleach

This powder is often used for cleaning laundry but can also be used for pottery. You can also purchase a liquid form of oxygen bleach. Mix in the powder with hot water and stir thoroughly. Allow it to cool, and then place the dishes in the mixture and let them soak for a few hours.

How do I know if my glaze has lead in it?

Lead-containing glazes or decorations on the outside of dishes or non-food surfaces are generally safer to use. The only way to determine if certain crockery has lead is to test it. Home test kits can tell you if the dishes have leachable lead. These tests are most useful in detecting high levels of lead.

What to add to glaze to make it brushable?

CMC gum is a ceramic glaze additive that can be used to help improve brushability in glazes that are mixed for dipping. Not only can CMC gum help improve brushability, but it can also help potters get better results when stamping glazes.

When did they stop putting lead in glaze?

If you are using dinnerware manufactured prior to 1971 or manufactured in another country, be sure there are no cracks, chips or damage to the glaze finish where lead can leach out, and look for a label that says it is safe for food use.

How can you tell if a glaze is food safe?

To test a glaze's acid resistance, squeeze a lemon wedge onto a horizontal, glazed surface. Changes in the glaze color indicate that acids from foods can leach materials from the glaze, and that it is not food safe.